MongoRepository doesn't support this; that is because MongoRepository is simply a Repository pattern implementation (e.g. abstraction layer) on top of the Mongo C# driver; specifying which fields to write/update is of no concern to a ("generic") repository
implementation (e.g it is an implementation-specific (mongodb) concern). You are, however, ofcourse free to simply use (and reference) the
mongocsharpdriver directly (which is installed and referenced anyway by the MongoRepository package).